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Besides being nicer code this also has the advantage of not making assumptions about the internal implementation: While it is documented that the AVFilter.inputs and AVFilter.outputs arrays are terminated by a zeroed sentinel, one is not allowed to infer that one can just check avfilter_pad_get_name(padarray, i) to see whether one has reached the sentinel: It could be that the pointer to the string is contained in a different structure than AVFilterPad that needs to be accessed first: return pad->struct->string. It could be that for small strings an internal buffer in AVFilterPad is used (to avoid a relocation) whereas for longer strings an external string is used; this is useful to avoid relocations: return pad->string_ptr ? pad->string_ptr : pad->interal_string Or it could be that the name has a default value: return pad->name ? pad->name : "default" (This actually made sense for us because the name of most of our AVFilterPads is just "default"; doing so would save lots of relocations.) The only thing one is allowed to infer from the existence of the sentinel is that one is allowed to use avfilter_pad_count() to get the number of pads. Therefore it is used. Reviewed-by: Nicolas George <george@nsup.org> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides a mean to alter decoded Audio and Video through chain of filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
- ffplay is a minimalistic multimedia player.
- ffprobe is a simple analysis tool to inspect multimedia content.
- Additional small tools such as
aviocat,ismindexandqt-faststart.
Documentation
The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Examples
Coding examples are available in the doc/examples directory.
License
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
Contributing
Patches should be submitted to the ffmpeg-devel mailing list using
git format-patch or git send-email. Github pull requests should be
avoided because they are not part of our review process and will be ignored.